As a conventional spring manufacturing apparatus, according to one arrangement, a plurality of tools are radially arranged on a forming table at an angular interval of 90°, and the respective tools can be driven by a single gear (for example, Teijin Seiki K. K., “Multi-Forming Machine ZUB-360 Type” fabricated 1972-10).
According to another spring manufacturing apparatus, a plurality of tools are radially arranged on a forming table at an angular interval of 45° about a wire to be fed out into a spring forming space above the forming table as the center. The respective tools are supported by tool support mechanisms, and are driven by servo motors independently of each other. With this arrangement, springs having various types of shapes can be formed by numerical control (for example, see Japanese Patent No. 2675523).
According to still another spring manufacturing apparatus, a plurality of tools are radially arranged on a forming table about a wire to be fed out into a spring forming space above the forming table as the center. The respective tools are supported by tool support mechanisms, and are driven by servo motors independently of each other. The forming table is circular, and the respective tool support mechanisms can be arranged on the peripheral portion of the forming table at arbitrary angles. Therefore, the angles of arrangement of the tools about the wire as the center can be finely adjusted (for example, see Japanese Patent No. 2690704).
According to still another spring manufacturing apparatus, a wire feed mechanism for feeding a wire into a spring forming space above a forming table can be rotated about a wire axis as the center. When the wire is rotated, the same effect as that obtained by changing the angles of arrangement of the tools about the wire as the center can be obtained (for example, see Japanese Patent No. 2939472).
The conventional spring apparatuses described above have made progress and development while they have solved the problems of how to make it easier to change the forming direction for the wire in an arbitrary direction and how to increase the degree of freedom in changing to the arbitrary direction.
In the conventional spring manufacturing apparatuses, servo motors are mounted on the respective tool support mechanisms so that the respective tools can be controlled independently of each other. Also, in addition to the servo motors for driving the tools, a wire feed roller for feeding out the wire and a servo motor for rotating a wire feed mechanism are necessary. Although the controllability and formability increase due to an increase in number of tools and the newly added function, the increase in number of servo motors increases the apparatus cost.
When removing a tool support mechanism from the forming table, the corresponding servo motor is also removed simultaneously. When finely adjusting the angle of arrangement of a tool, the corresponding servo motor is also moved simultaneously. As the tool support mechanism is heavy, the operability is poor.
The apparatuses may be selectively used in accordance with applications. For example, when forming a spring having a complicated shape by forming, an apparatus having a large number of servo motors and thus having a high formability may be used. When forming a spring having a simple shape by forming, an inexpensive, simple apparatus having a small number of servo motors may be used. Consequently, an apparatus which has a high formability but is inexpensive because the number of servo motors is reduced is sought for.